Process for producing aqueous surfactant concentrates

ABSTRACT

The invention concerns aqueous surfactant concentrates having a solids content of between 35 and 65 wt % and containing (a1) alkyl oligoglycosides and/or alkenyl oligoglycosides; and/or (a2) fatty acid N-alkylpolyhydroxy alkylamides; and (b) betaine, in weight ratios of (a):(b) of between 10:90 and 90:10; wherein the pH of these concentrates is between 3.5 and 6.5.

FIELD OF THE INVENTION

This invention relates to a process for the production of aqueoussurfactant concentrates containing selected sugar surfactants andbetaines which are distinguished by improved performance properties.

DISCUSSION OF THE RELATED ART

Sugar surfactants, such as for example alkyl oligoglycosides and, moreparticularly, alkyl oligoglucosides, are nonionic surfactants which areacquiring increasing significance by virtue of their excellent detergentproperties and their high ecotoxicological compatibility. The productionand use of these substances have been described just recently in anumber of synoptic articles, of which the articles by H. Hensen in SkinCare Forum, 1, (October 1992), D. Balzer and N. Ripke inSeifen-Ole-Fette-Wachse 118, 894 (1992) and B. Brancq inSeifen-Ole-Fette-Wachse 118, 905 (1992) are cited as examples. The sameapplies to a second group of sugar surfactants, namely fattyacid-N-alkyl polyhydroxyalkylamides and preferably fatty acid-N-alkylglucamides.

Various binary mixtures of sugar surfactants of the type mentioned withother surfactants are known from the prior art. Among these surfactantcompounds, combinations of sugar surfactants, more particularly alkyloligoglucosides, with betaines occupy a special position because foamingand cleaning power and also skin-cosmetic compatibility are improvedover a broad molar fraction range. For example, German patentapplication DE-A1 42 34 487 (Henkel) describes a manual dishwashingdetergent containing fatty alcohol sulfates and fatty alcohol ethersulfates in addition to alkyl glucosides and betaines. According to theteaching of DE-A1 43 11 114 (Henkel), mixtures of alkyl glucosides,betaines and selected fatty alcohol polyglycol ethers may be used forthe same purpose. Finally, DE-A1 40 09 616 (Henkel) describes liquidbody-are formulations containing protein fatty acid condensates inaddition to alkyl glucosides and betaines.

However, all the known formulations are more or less dilute aqueoussolutions whereas the objective of any manufacturer of alkylglucoside/betaine mixtures must be to make highly concentrated productswhich afford distinct advantages in regard to storage. Unfortunately,the production of corresponding concentrates is attended by a number ofdisadvantages: mixtures of alkyl glucosides and betaines which aregenerally alkaline from their production are viscous and often cloudy atsolids contents of 40 to 60% by weight. In addition, their stability instorage is not always satisfactory, i.e. their viscosity can continue toincrease with time through the formation of liquid crystalline gelphases and/or the products undergo crystallization. This naturally leadsto a very considerable reduction in the economic value of correspondingconcentrates.

Accordingly, the complex problem addressed by the present invention wasto provide a process for the production of binary surfactantconcentrates which would be free from the disadvantages mentioned above.

DESCRIPTION OF THE INVENTION

The present invention relates to a process for the production ofwater-containing surfactant concentrates with a solids content of 35 to65% by weight and preferably 40 to 60% by weight, containing

(a1) alkyl and/or alkenyl oligoglycosides and/or

(a2) fatty acid-N-alkyl polyhydroxyalkylamides and

(b) betaines

in a ratio by weight of (a) to (b) of 10:90 to 90:10, characterized inthat the concentrates are adjusted to a pH value of 3.5 to 6 andpreferably 4 to 6.

It has surprisingly been found that mixtures of sugar surfactants andbetaines, which are normally viscous and cloudy at alkaline pH values,readily become low in viscosity and clear when the pH value of themixtures is reduced to the acidic range. This measure also has apositive effect on the stability of the products in storage, i.e. theconcentrates show a constant low viscosity, even in the event ofprolonged storage, and have relatively little tendency towardscrystallization. The present invention also includes the observationthat viscous surfactant concentrates can be reduced in their viscosityand clouding can be eliminated by subsequent adjustment of the pH value.

Alkyl and/or Alkenyl Oligoglycosides

Alkyl and alkenyl oligoglycosides are known substances which correspondto general formula (I):

    R.sup.1 O-(G).sub.p                                        (I)

where R¹ is an alkyl and/or alkenyl radical containing 4 to 22 carbonatoms, G is a sugar unit containing 5 or 6 carbon atoms and p is anumber of 1 to 10, and which may be obtained by the relevant methods ofpreparative organic chemistry. EP-A-1-0 301 298 and WO 90/03977 arecited as representative of the extensive literature available on thissubject.

The alkyl and/or alkenyl oligoglycosides may be derived from aldoses orketoses containing 5 or 6 carbon atoms, preferably glucose. Accordingly,the preferred alkyl and/or alkenyl oligoglycosides are alkyl and/oralkenyl oligoglucosides.

The index p in general formula (I) indicates the degree ofoligomerization (DP degree), i.e. the distribution of mono- andoligoglycosides, and is a number of 1 to 10. Whereas p in a givencompound must always be an integer and, above all, may assume a value of1 to 6, the value p for a certain alkyl oligoglycoside is ananalytically determined calculated quantity which is generally a brokennumber. Alkyl and/or alkenyl oligoglycosides having an average degree ofoligomerization p of 1.1 to 3.0 are preferably used. Alkyl and oralkenyl oligoglycosides having a degree of oligomerization of less than1.7 and, more particularly, between 1.2 and 1.4 are preferred from theapplicational point of view.

The alkyl or alkenyl radical R¹ may be derived from primary alcoholscontaining 4 to 11 and preferably 8 to 10 carbon atoms. Typical examplesare butanol, caproic alcohol, caprylic alcohol, capric alcohol andundecyl alcohol and the technical mixtures thereof obtained, forexample, in the hydrogenation of technical fatty acid methyl esters orin the hydrogenation of aldehydes from Roelen's oxosynthesis. Alkyloligoglucosides having a chain length of C₈ to C₁₀ (DP=1 to 3), whichare obtained as first runnings in the separation of technical C₈₋₁₈cocofatty alcohol by distillation and which may contain less than 6% byweight of C₁₂ alcohol as an impurity, and also alkyl oligoglucosidesbased on technical C_(9/11) oxoalcohols (DP=1 to 3) are preferred.

In addition, the alkyl or alkenyl radical R¹ may also be derived fromprimary alcohols containing 12 to 22 and preferably 12 to 14 carbonatoms. Typical examples are lauryl alcohol, myristyl alcohol, cetylalcohol, palmitoleyl alcohol, stearyl alcohol, isostearyl alcohol, oleylalcohol, elaidyl alcohol, petroselinyl alcohol, arachyl alcohol,gadoleyl alcohol, behenyl alcohol, erucyl alcohol and technical mixturesthereof which may be obtained as described above. Alkyl oligoglucosidesbased on hydrogenated C_(12/14) cocofatty alcohol having a DP of 1 to 3are preferred.

Fatty acid-N-alkyl polyhydroxyalkylamides

Fatty acid-N-alkyl polyhydroxyalkylamides correspond to formula (II):##STR1## in which R² CO is an aliphatic acyl radical containing 6 to 22carbon atoms, R³ is hydrogen, an alkyl or hydroxyalkyl radicalcontaining 1 to 4 carbon atoms and Z! is a linear or branchedpolyhydroxyalkyl radical containing 3 to 12 carbon atoms and 3 to 10hydroxyl groups.

The fatty acid-N-alkyl polyhydroxyalkylamides are known compounds whichmay normally be obtained by reductive amination of a reducing sugar withammonia, an alkylamine or an alkanolamine and subsequent acylation witha fatty acid, a fatty acid alkyl ester or a fatty acid chloride.Processes for their production are described in U.S. Pat. No. 1,985,424,in U.S. Pat. No. 2,016,962 and in U.S. Pat. No. 2,703,798 and inInternational patent application WO 92/06984. An overview of thissubject by H. Kelkenberg can be found in Tens. Surf. Det. 25, 8 (1988).

The fatty acid-N-alkyl polyhydroxyalkylamides are preferably derivedfrom reducing sugars containing 5 or 6 carbon atoms, more particularlyfrom glucose. Accordingly, the preferred fatty acid-N-alkylpolyhydroxyalkylamides are fatty acid-N-alkyl glucamides whichcorrespond to formula (III): ##STR2##

Preferred fatty acid-N-alkyl polyhydroxyalkylamides are glucamidescorresponding to formula (III) in which R³ is hydrogen or an alkyl groupand R² CO represents the acyl component of caproic acid, caprylic acid,capric acid, lauric acid, myristic acid, palmitic acid, palmitoleicacid, stearic acid, isostearic acid, oleic acid, elaidic acid,petroselic acid, linoleic acid, linolenic acid, arachic acid, gadoleicacid, behenic acid or erucic acid or technical mixtures thereof. Fattyacid-N-alkyl glucamides (III) obtained by reductive amination of glucosewith methylamine and subsequent acylation with lauric acid or C_(12/14)cocofatty acid or a corresponding derivative are particularly preferred.In addition, the polyhydroxyalkylamides may also be derived from maltoseand palatinose.

Betaines

Betaines are known surfactants which are mainly produced bycarboxyalkylation, preferably carboxymethylation, of aminic compounds.The starting materials are preferably condensed with halo carboxylicacids or salts thereof, more particularly with sodium chloroacetate, 1mole of salt being formed per mole of betaine. The addition ofunsaturated carboxylic acids, such as acrylic acid for example, is alsopossible. Information on the nomenclature and, in particular, thedifference between betaines and "true" amphoteric surfactants can befound in the Article by U, Ploog in Seifen-Oe-Fette-Wachse, 198, 373(1982). Further information on this subject can be found, for example,in A. O'Lennick et al., HAPPI, November 70 (1986), in S. Holzman et al.,Tens. Det. 23, 309 (1986), in R. Bibo et al. Soap Cosm. Chem. Spec.April 46 (1990) and in P. Ellis et al., Euro Cosm. 1, 14 (1994).

Examples of suitable betaines are the carboxyalkylation products ofsecondary and, in particular, tertiary amines which correspond toformula (IV): ##STR3## in which R⁴ represents alkyl and/or alkenylradicals containing 6 to 22 carbon atoms, R⁵ is hydrogen or alkylradicals containing 1 to 4 carbon atoms, R⁶ represents alkyl radicalscontaining 1 to 4 carbon atoms, n is a number of 1 to 6 and X is analkali metal and/or alkaline earth metal or ammonium.

Typical examples are the carboxymethylation products of hexylmethylamine, hexyl dimethylamine, octyl dimethyl amine, decyldimethylamine, dodecyl methylamine, dodecyl dimethylamine, dodecyl ethylmethylamine, C_(12/14) cocoalkyl dimethylamine, myristyl dimethylamine,cetyl dimethylamine, stearyl dimethylamine, stearyl ethyl methylamine,oleyl dimethylamine, C_(16/18) tallow alkyl dimethylamine and technicalmixtures thereof.

Also suitable are carboxyalkylation products of amidoaminescorresponding to formula (V): ##STR4## in which R⁷ CO is an aliphaticacyl radical containing 6 to 22 carbon atoms and 0 or 1 to 3 doublebonds, m is a number of 1 to 3 and R⁵, R⁶, n and X are as defined above.

Typical examples are reaction products of fatty acids containing 6 to 22carbon atoms, namely caproic acid, caprylic acid, capric acid, lauricacid, myristic acid, palmitic acid, palmitoleic acid, stearic acid,isostearic acid, oleic acid, elaidic acid, petroselic acid, linoleicacid, linolenic acid, elaeostearic acid, arachic acid, gadoleic acid,behenic acid and erucic acid and technical mixtures thereof, withN,N-dimethyl aminoethylamine, N,N-dimethyl amino-propylamine,N,N-diethyl aminoethylamine and N,N-diethyl aminopropylamine which arecondensed with sodium chloroacetate. It is preferred to use acondensation product of C_(8/18) cocofatty acid N,N-dimethylaminopropylamide with sodium chloroacetate.

Other suitable starting materials for the betaines to be used inaccordance with the invention are imidazolines corresponding to formula(VI): ##STR5## in which R⁸ is an alkyl radical containing 5 to 21 carbonatoms, R⁹ is a hydroxyl group, an OCOR⁸ or NHCOR⁸ group and m=2 or 3.These substances are also known substances which may be obtained, forexample, by cyclizing condensation of 1 or 2 moles of fatty acid withpolyfunctional amines such as, for example, aminoethyl ethanolamine,(AEEA) or diethylene triamine. The corresponding carboxyalkylationproducts are mixtures of different open-chain betaines.

Typical examples are condensation products of the above-mentioned fattyacids with AEEA, preferably imidazolines based on lauric acid or, again,C_(12/14) cocofatty acid which are subsequently betainized with sodiumchloroacetate.

Surfactant Concentrates

The surfactant concentrates are aqueous solutions or pastes having asolids content of 40 to 60% by weight and preferably 45 to 55% byweight. Components (a) and (b) may be present in the concentrates in aratio by weight of 90:10 to 10:90, preferably 80:20 to 20:80 and, morepreferably, 60:40 to 40:60.

The surfactant compounds may be produced in various ways. For example,dilute solutions of the sugar surfactants and the betaines may be mixedand subsequently concentrated. However, it is better to mix theconcentrates, thereby eliminating the need for the complicated removalof water from the mixtures. Finally, the concentrates are directlyobtained in the production of the betaines providing the quaternizationof the tertiary amines on which the betaines are based is carried out inthe presence of the water-containing sugar surfactants as solvent. Thetime at which the pH value is adjusted is not critical. It is evenpossible subsequently to convert viscous, cloudy concentrates intoproducts of satisfactory performance. The pH value is preferablyadjusted by addition of mineral acids such as, for example, hydrochloricacid, sulfuric acid or, preferably, phosphoric acid or organic acids,such as lactic acid, citric acid and the like. C₈₋₁₈ and preferablyC₁₂₋₁₄ fatty acids liquid at room temperature, such as lauric acid oroleic acid for example, may also be used for the same purpose.

Commercial Applications

By reducing the pH value, it is possible over a broad molar fractionrange to produce concentrates of sugar surfactants and betaines whichhave a low viscosity favorable for handling, which are clear and whichshow increased stability in storage. The concentrates are suitable forthe production of surface-active formulations, such as in particularmanual dishwashing detergents and hair shampoos.

The following Examples are intended to illustrate the invention withoutlimiting it in any way.

EXAMPLES

    ______________________________________    I.     Surfactants used    ______________________________________    A1)    C.sub.8/10 alkyl oligoglucoside (Plantaren ® APG 225)    A2)    C.sub.12/16 alkyl oligoglucoside (Plantaren ® APG 1200)    A3)    C.sub.8/16 alkyl oligoglucoside (Plantaren ® APG 2000)    A4)    Mixture of A1 and A3 (60:40 parts by weight)    A5)    Mixture of A1 and A3 (80:20 parts by weight)    A6)    Mixture of A1 and A3 (75:25 parts by weight)    A7)    Mixture of A1 and A3 (50:50 parts by weight)    A8)    Mixture of A1 and A3 (43:57 parts by weight)    A9)    Cocofatty acid N-methyl glucamide    B1)    Betaine based on fatty acid aminoamide (Dehyton ® PK 45)    B2)    Betaine based on tertiary amine (Dehyton ® AB    ______________________________________           30)

II. Performance Test Results

The mixtures of Examples 1 to 13 were adjusted to a solids content of50% by weight and to a pH value of 4 to 6. The viscosity of the productswas determined by the Brookfield method (20° C., 10 r.p.m., spindle 2)both immediately and after storage for 6 months at 10° C. Appearance wasvisually evaluated after storage for 10 days. The products of ComparisonExamples C1 to C4 were treated in the same way, but adjusted to analkaline pH value. The results are set out in Table 1 (percentages as %by weight).

                  TABLE 1    ______________________________________    Viscosity measurements and storage tests                 SC           Vis.  mPa · s!    Ex.  A      B       A:B  %    pH    1 h   6 m  Prod.    ______________________________________    1    A1     B1      25:75                             51   4.2    500   550 Clear    2    A1     B1      50:50                             56   5.6   2700  2800 Clear    3    A1     B1      75:25                             62   5.7   6150  6175 Clear    4    A2     B2      50:50                             50   5.0   3000  3100 Clear    5    A3     B1      25:75                             40   5.0    250   275 Clear    6    A3     B1      50:50                             44   4.7   1500  1550 Clear    7    A3     B1      75:25                             47   4.2   1200  1300 Clear    8    A4     B1      57:43                             54   5.1   3100  3200 Clear    9    A5     B1      59:41                             55   5.4   3000  3100 Clear    10   A6     B1      48:52                             53   5.5   2400  2500 Clear    11   A7     B1      67:33                             55   5.1   3100  3200 Clear    12   AB     B1      75:25                             56   5.1   2900  3000 Clear    13   A9     B1      50:50                             50   5.0   1200  1250 Clear    C1   A1     B1      50:50                             56   10.8  6000  --   Cloudy    C2   A2     B2      50:50                             50   9.5   7500  --   Cloudy    C3   A3     B1      75:25                             47   11.0  1700  --   Cloudy    C4   A3     B1      50:50                             48   10.0  6600  --   Cloudy    ______________________________________     Legend:     SC = Solids content     Vis. = Viscosity     Prod. = Appearance of the product

The products obtained by the process according to the invention show aconstant, low viscosity and remain clear, even after storage for 6months. By contrast the comparison products accumulate in the form ofviscous, cloudy mixtures during their production and either crystallizeor continue to thicken in storage.

What is claimed is:
 1. A process for preparing a stable aqueoussurfactant concentrate comprising combining in an aqueous medium a sugarsurfactant comprising an alkyl or alkenyl oligoglycoside or a fattyacid-N-alkyl polyhydroxyalkylamide and a betaine, wherein the sugarsurfactant and betaine together comprise 40% to 65% by weight of theconcentrate and are present in the concentrate in a weight ratio of10:90 to 90:10, and adjusted the pH of the aqueous medium to 3.5 to 6.5.2. A process according to claim 1, wherein the sugar surfactant and thebetaine together comprise 40% to 60% by weight of the concentrate.
 3. Aprocess according to claim 1, wherein the sugar surfactant and betaineare present in the concentrate in a weight ratio of 80:20 to 20:80.
 4. Aprocess according to claim 3, wherein the sugar surfactant and thebetaine are present in the concentrate in a weight ratio of 60:40 to40:60.
 5. A process according to claim 1, wherein the pH is adjusted bythe addition of an acid selected from the group consisting ofhydrochloric acid, sulfuric acid, phosphoric acid, lactic acid, citricacid, lauric acid, and oleic acid.
 6. A process according to claim 1,wherein the oligoglycoside is a compound of the formula (I):

    R.sup.1 O-(G).sub.p                                        (I)

wherein R¹ is C₄ to C₂₂ alkyl or alkenyl, G is a sugar unit having 5 or6 carbon atoms, and p is a number of 1 to
 10. 7. A process according toclaim 1, wherein the fatty acid-N-alkylpolyhydroxyalkylamide is acompound of formula (II): ##STR6## wherein R² CO is C₆ to C₂₂ aliphaticacyl, R³ is hydrogen, C₁ to C₄ alkyl, or C₁ to C₄ hydroxyalkyl, and Z islinear or branched C₃ to C₁₀ polyhydroxyalkyl having 3 to 10 hydroxylgroups.
 8. A process according to claim 1, wherein the betaine is acompound of the formula (IV): ##STR7## wherein R⁴ is C₆ to C₂₂ alkyl oralkenyl, R⁵ is hydrogen or C₁ to C₄ alkyl, R⁶ is C₁ to C₄ alkyl, n is anumber of 1 to 6, and X is alkali metal, alkaline earth metal, orammonium.
 9. A process according to claim 1, wherein the betaine is acompound of the formula (V): ##STR8## wherein R⁷ CO is C₆ to C₂₂aliphatic acyl having 0 to 3 double bonds, R⁵ is hydrogen or C₁ to C₄alkyl, R⁶ is C₁ to C₄ alkyl, m is a number of 1 to 3, n is a number of 1to 6, and X is alkali metal, alkaline earth metal, or ammonium.